The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In a four-stroke naturally aspirated engine, the theoretical maximum amount of air that each cylinder can ingest during the intake cycle is equal to the swept volume of the cylinder. Since each cylinder has one intake stroke every two revolutions of the crankshaft, the theoretical maximum volume of air ingested during each rotation of the crankshaft is equal to one-half the displacement. The actual amount of air that the engine ingests compared to the theoretical maximum is called volumetric efficiency (VE).
There are many factors that determine the amount of torque an engine can produce and the RPM at which the maximum torque occurs. One determinant is the mass of air the engine can ingest into the cylinders. There is a strong relationship between VE and maximum torque. Generally, the RPM at peak VE coincides with the RPM at the torque peak.
VE has been calculated using lookup tables for engines without intake and exhaust cam phasers. Lookup tables can be cumbersome when intake and exhaust cam phasers are added. Mathematical relationships can be used to handle the complexity of VE with intake and exhaust cam phasers. However, mathematical relationships tend to increase calibration effort and time. Accuracy may also be reduced.